Process of making aluminous abrasives.



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' To all whom it may concern:

subject of the King of Great Britain, residand crystallize.

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THOMAS B. ALLEN, 0F TORONTO, CANADA, ASSIG-NOR TO THE CARBORUNDUM COMP, OF NIAGARA FALLS, NEW YORK, A- CORPORATION OF PENNSYLVANIA.

PROCESS OF MAKING ALUMINOUS ABRASIVES. I

Specification of Letters Patent. Patented June 4, 1918.

Serial N0. 130,788.

No Drawing. Application filed November 11, 1916.

supply of electric energy and other necessities exists.

I have discovered that I can produce a ing at Toronto, Canada, have invented a crystalline artificial aluminous abrasive manew and useful Improvement in Processes terial resembling natural emery in some of Making Aluminous Abrasives, of which characteristicsand can avoid all the difiithe following is a full, clear, and exact deculty inherent in electrically prepared abrascription. sives by subjecting aluminous ore or alumi- This invention relates to a new and usenous mixture to fuel heat or heat generated ful improvement in the manufacture of aluin a combustion furnace and l have found minous abrasives, Aluminous abrasives that the combustion of fuel, .oil preferably, are now commonly made by the use of an under strongly reducing conditions gives electrically developed heat process usually good results in this method. In choosing a consisting in subjecting aluminous ore such suitable mixture for melting, it is necessary as emery, bauxite or clay, usually with the to consider the abrasive qualities such as addition of a reducing agent, such as carbon, hardness, toughness and fracture that are deto heat in an electric furnace until the prodsired. These properties are determined by not is fused and then allowin it to cool the proportion of the components of the mix- These electrically prepared ture and by the chemical composition of the abrasives have a wide field of usefulness,

components. I have found that substances nevertheless despite their great eificlency containing from to 85% of alumina, they have not succeeded in displacing the and 10% to 20% iron oxid, 3% to 10% of natural emery in a variety of grinding and silica and 2% to 5% titanium oxid yield a polishing operations since they are distinsatisfactory product. I prefer to take as a. guished from the latter not only in their raw material a bauxite ore consisting after chemical composition but also in their calcining of about 80% alumina, 10% iron physical properties. They are in general of oxid, 7% silica and 3% titanium oxid. Such greater hardness and toughness than natural an ore is readily selected from available emery and for th1s reason certain grindlng bauxite ores or may be arrived at by mixing operations are best accomplished by the natural abrasive and with more economical realuminous ores with the other above mensults.

tioned components. The materials are re- L duced to a fine state of sub-division so that In the manufacture of artificial abrasives by electrically developed heat there are alall will pass through a i inch mesh and pref ways present both in microscopic and macerably finer. -After thoroughly mixing the roscopic amounts certain impurities usually are fed into a fuel heated urnace by whic of a metallic nature or having the charactera thorough heating and a partial sinteristics of reduction products, which result Be it known that I, THOMAS B. ALLEN, a

ing may be effected. For this purpose I have found a rotary kiln lined with a suitfrom the reduction of impurities in the able refractory lining to be preferable, this aluminous ore either by addedcarbonaceous acting as a pre-heater. The thoroughly material or by the action of the electrodes. heated or partially sintered material is then These impurities are usually compounds of placed in a crucible in which the final heatmetallic iron with silicon titanium or other ing is accomplished. By means of oil flame elements and must be substantially removed a temperature of 3400F. may be obtained before an abrasive of satisfactory properties and I find this is sufiicient to efiect the furcan be produced, because usually their presther and final fusion of the material. I find ence causes great d'ifiiculty in the manufacit is not necessary to have the materlal ture of suitable grinding and polishing artibrought to a very liquid state, indeed for cles, especially in the proper binding of the many purposes merely obtaining the mateabrasive grain. Furthermore, electrically rial in a molten state is sufficient to yield a prepared abrasives are very expensive, due satisfactory product. If desired, the preto the high cost of electrodes, electric energy heating can be dispensed with and the enand the maintenance cost of electric furnace tire operation accomplished in a slngle stage with the oil fuel. During the preheatlng operations. Moreover, their manufacture is limited to those regions where a plentiful and in the final heating it is preferable to have a strongly reducing atmosphere in order that the iron oxid present assume a ferrous state in which state it has a much greater fluxing power than when in the higher state of oxidation. A final melting may be made in a graphite crucible or in a vessel lined with a suitable refractory material and the heat may be supplied indirectly or directly.

I .do not limit myself to the methodof heating here described, and in carrying out the operation on a large scale the heat may be accomplished by playing several jets of the oil flame upon the surface of the mass to be heated, the new material being dropped on in owdered form under the flame and an ingot e built up making the process practica ly continuous. The oil flame may be displaced with a flame of powdered coal or gas. I

The material crystallizes on cooling, forming a dark crystalline mass characterized by great hardness. Its toughness is dependent on the components of the mixture, on the size of the ingot formed, the rate of cooling and the degree of temperature attained and may be varied depending on the uses to which the product is to be put. The product exhibits rough surfaces on fracture which aid in its use as a olishing material when same is glued on to dloth or polishing wheels. The product is free from impurities such as reduction products containing iron andafter crushing to a suitable degree of fineness and sifting may be made upwithout.

further treatment into abrasive wheels, blocks, etc. This results in great economy its manufacture.

The present invention is not limited to the details of procedure hereinbefore set forth, but may be practised with various variations within the scope of the following claims. Y

I claim:

1. The process of making crystalline aluminous abrasives, which comprises subvlib jecting an aluminous ore, the major portion of which consists of-alumina and which con-- tains fifteen per cent. or more of iron oxid and silica to fuel heat in a reducing atmosphere an of a character to fuse the -material, substantially as described. I

2. The process of making crystalline aluminous abrasives, which comprises the steps of subiecting a mixture, the major portion of which consists of alumina and which contains fifteen per cent. or more of iron oxid and silica, to a high temperature produced by fuel heat under strong reducing conditions sufficient to cause the mixture to fuse, and then allowing the fused mass to cool and crystallize, substantially as described. I

.3. The process of making crystalline aluminous abrasives, comprising the steps of heating a mixture composed mainly of alumina and containing more than ten per cent. of lI'OIl oxid and sllica until smtermg occurs, subjecting the sintered mass to fuel crystallize, substantially as described.

5. In the manufacture of crytalline aluminous abrasives, the method which consists in preheating'a mixture composed mainly of alumina and containing fifteen per cent. or more of iron oxid and silica until partial sintering occurs, and then subjecting the partially sintered mass 'to further heat sufficient to fuse it, substantially as described.

of making crystalline 6. The process of making crystalline aluminous abrasives, which consists in preheating an alumlnous material. consisting mainly of alumina containing fifteen per cent. or more of iron oxid or silica, fusing the preheated mixture by fuel heat, and allowing the fused mass to cool and crystallize, substantially as described.

' 7. The process of making crystalline aluminous abrasives, comprising the steps of rectly to an aluminous material, consisting mainly of alumina and containing fifteen per cent. or more of iron oxid and silica to fuse the same, and allowing the fused mass to cool and crystallize, substantially as de scribed.

In testimony whereof, I have hereunto set my hand.

. THOMAS B; ALLEN. Witnesses:

I applying the heat of fuel combustion di- 

